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.TH T_ALLOC 3NSL "May 7, 1998"
.SH NAME
t_alloc \- allocate a library structure
.SH SYNOPSIS
.LP
.nf
#include <xti.h>




\fBvoid *\fR\fBt_alloc\fR(\fBint\fR \fIfd\fR, \fBint\fR \fIstruct_type\fR, \fBint\fR \fIfields\fR);
.fi

.SH DESCRIPTION
.sp
.LP
This routine is part of the \fBXTI\fR interfaces which evolved from the
\fBTLI\fR interfaces. \fBXTI\fR represents the future evolution of these
interfaces. However, \fBTLI\fR interfaces are supported for compatibility. When
using a \fBTLI\fR routine that has the same name as an \fBXTI\fR routine, a
different header file, \fBtiuser.h\fR, must be used.  Refer to the section,
\fBTLI\fR \fBCOMPATIBILITY\fR, for a description of differences between the two
interfaces.
.sp
.LP
The \fBt_alloc()\fR function dynamically allocates memory for the various
transport function argument structures as specified below. This function will
allocate memory for the specified structure, and will also allocate memory for
buffers referenced by the structure.
.sp
.LP
The structure to allocate is specified by \fIstruct_type\fR and must be one of
the following:
.sp
.in +2
.nf
T_BIND		    struct	t_bind
T_CALL		    struct	t_call
T_OPTMGMT		 struct	t_optmgmt
T_DIS			    struct	t_discon
T_UNITDATA		struct	t_unitdata
T_UDERROR		 struct	t_uderr
T_INFO		    struct	t_info
.fi
.in -2

.sp
.LP
where each of these structures may subsequently be used as an argument to one
or more transport functions.
.sp
.LP
Each of the above structures, except  \fBT_INFO,\fR contains at least one field
of type \fBstruct\fR \fBnetbuf\fR. For each field of this type, the user may
specify that the buffer for that field should be allocated as well. The length
of the buffer allocated will be equal to or greater than the appropriate size
as returned in the \fIinfo\fR argument of \fBt_open\fR(3NSL) or
\fBt_getinfo\fR(3NSL). The relevant fields of the \fIinfo\fR argument are
described in the following list. The \fIfields\fR argument specifies which
buffers to allocate, where the argument is the bitwise-or of any of the
following:
.sp
.ne 2
.na
\fB\fBT_ADDR\fR \fR
.ad
.RS 12n
The \fIaddr\fR field of the \fBt_bind\fR, \fBt_call\fR, \fBt_unitdata\fR or
\fBt_uderr\fR structures.
.RE

.sp
.ne 2
.na
\fB\fBT_OPT\fR \fR
.ad
.RS 12n
The \fIopt\fR field of the \fBt_optmgmt\fR, \fBt_call\fR, \fBt_unitdata\fR or
\fBt_uderr\fR structures.
.RE

.sp
.ne 2
.na
\fB\fBT_UDATA\fR \fR
.ad
.RS 12n
The \fIudata\fR field of the \fBt_call\fR, \fBt_discon\fR or \fBt_unitdata\fR
structures.
.RE

.sp
.ne 2
.na
\fB\fBT_ALL\fR \fR
.ad
.RS 12n
All relevant fields of the given structure. Fields which are not supported by
the transport provider specified by \fIfd\fR will not be allocated.
.RE

.sp
.LP
For each relevant field specified in \fIfields\fR, \fBt_alloc()\fR will
allocate memory for the buffer associated with the field, and initialize the
\fIlen\fR field to zero and the \fIbuf\fR pointer and \fImaxlen\fR field
accordingly. Irrelevant or unknown values passed in fields are ignored. Since
the length of the buffer allocated will be based on the same size information
that is returned to the user on a call to \fBt_open\fR(3NSL) and
\fBt_getinfo\fR(3NSL), \fIfd\fR must refer to the transport endpoint through
which the newly allocated structure will be passed. In the case where a
\fBT_INFO\fR structure is to be allocated, \fIfd\fR may be set to any value. In
this way the appropriate size information can be accessed. If the size value
associated with any specified field is  \fBT_INVALID,\fR \fBt_alloc()\fR will
be unable to determine the size of the buffer to  allocate and will fail,
setting  \fBt_errno\fR to \fBTSYSERR\fR and  \fBerrno\fR to \fBEINVAL\fR.  See
\fBt_open\fR(3NSL) or  \fBt_getinfo\fR(3NSL). If the size value associated with
any specified field is  \fBT_INFINITE,\fR then the behavior of  \fBt_alloc()\fR
is implementation-defined. For any field not specified in \fIfields\fR,
\fIbuf\fR will be set to the null pointer and \fIlen\fR and \fImaxlen\fR will
be set to zero. See  \fBt_open\fR(3NSL) or \fBt_getinfo\fR(3NSL).
.sp
.LP
The pointer returned if the allocation succeeds is suitably aligned so that it
can be assigned to a pointer to any type of object and then used to access such
an object or array of such objects in the space allocated.
.sp
.LP
Use of \fBt_alloc()\fR to allocate structures will help ensure the
compatibility of user programs with future releases of the transport interface
functions.
.SH RETURN VALUES
.sp
.LP
On successful completion, \fBt_alloc()\fR returns a pointer to the newly
allocated structure. On failure, a null pointer is returned.
.SH VALID STATES
.sp
.LP
ALL - apart from \fBT_UNINIT\fR
.SH ERRORS
.sp
.LP
On failure, \fBt_errno\fR is set to one of the following:
.sp
.ne 2
.na
\fB\fBTBADF\fR\fR
.ad
.RS 16n
\fBstruct_type\fR is other than  \fBT_INFO\fR and the specified file descriptor
does not refer to a transport endpoint.
.RE

.sp
.ne 2
.na
\fB\fBTNOSTRUCTYPE\fR\fR
.ad
.RS 16n
Unsupported \fIstruct_type\fR requested. This can include a request for a
structure type which is inconsistent with the transport provider type
specified, that is, connection-mode or connectionless-mode.
.RE

.sp
.ne 2
.na
\fB\fBTPROTO\fR\fR
.ad
.RS 16n
This error indicates that a communication problem has been detected between XTI
and the transport provider for which there is no other suitable XTI error
\fB(t_errno)\fR.
.RE

.sp
.ne 2
.na
\fB\fBTSYSERR\fR\fR
.ad
.RS 16n
A system error has occurred during execution of this function.
.RE

.SH TLI COMPATIBILITY
.sp
.LP
The \fBXTI\fR and \fBTLI\fR interface definitions have common names but use
different header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
.SS "Interface Header"
.sp
.LP
The \fBXTI\fR interfaces use the header file, \fBxti.h\fR. \fBTLI\fR interfaces
should \fInot\fR use this header.  They should use the header:
.sp
.LP
\fB#include\fR \fB<tiuser.h>\fR
.SS "Error Description Values"
.sp
.LP
The \fBt_errno\fR values that can be set by the \fBXTI\fR interface and cannot
be set by the \fBTLI\fR interface are:
.sp
.ne 2
.na
\fB\fBTPROTO\fR \fR
.ad
.RS 17n

.RE

.sp
.ne 2
.na
\fB\fBTNOSTRUCTYPE\fR \fR
.ad
.RS 17n

.RE

.SS "Special Buffer Sizes"
.sp
.LP
Assume that the value associated with any field of \fBstruct\fR \fBt_info\fR
(argument returned by \fBt_open()\fR or \fBt_getinfo()\fR\|) that describes
buffer limits is -1. Then the underlying service provider can support a buffer
of unlimited size.  If this is the case, \fBt_alloc()\fR will allocate a buffer
with the default size 1024 bytes, which may be handled as described in the next
paragraph.
.sp
.LP
If the underlying service provider supports a buffer of unlimited size in the
\fBnetbuf\fR structure (see \fBt_connect\fR(3NSL)), \fBt_alloc()\fR will return
a buffer of size 1024 bytes. If a larger size buffer is required, it will need
to be allocated separately using a memory allocation routine such as
\fBmalloc\fR(3C). The \fBbuf\fR and \fBmaxlen\fR fields of the \fBnetbuf\fR
data structure can then be updated with the address of the new buffer and the
1024 byte buffer originally allocated by \fBt_alloc()\fR can be freed using
\fBfree\fR(3C).
.sp
.LP
Assume that the value associated with any field of \fBstruct\fR \fBt_info\fR
(argument returned by \fBt_open()\fR or \fBt_getinfo()\fR \fB\|)\fR that
describes nbuffer limits is \fB-2\fR\&. Then \fBt_alloc()\fR will set the
buffer pointer to \fINULL\fR and the buffer maximum size to \fB0\fR, and then
will return success (see \fBt_open\fR(3NSL) or \fBt_getinfo\fR(3NSL)).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7)  for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR free (3C),
.BR malloc (3C),
.BR t_connect (3NSL),
.BR t_free (3NSL),
.BR t_getinfo (3NSL),
.BR t_open (3NSL),
.BR attributes (7)
